Greek Cypriot and Turkish Cypriot leaders have failed for a second day to agree on a U.N. mediated plan for reuniting their divided island. But a third day of talks is scheduled.

Greek Cypriot leader Tassos Papadopoulos and his Turkish counterpart Rauf Denktash met for less than 90 minutes Wednesday in U.N. Secretary General Kofi Annan's office. As they emerged separately from the meeting, they passed reporters without a word, except to say a third session would be held Thursday.

Adding to the mystery about what had happened, U.N. officials who briefed reporters after the first meeting Tuesday declined comment this time.

The rival leaders are known to be under fierce international pressure to accept a U.N. brokered process that could end 30 years of division on Cyprus in time to meet a May first deadline. U.N. diplomats have described the closed-door negotiations as intense.

Before Wednesday session, U.N. spokesman Fred Eckhard suggested the talks are at a delicate stage. He said Secretary General Annan, in an attempt to press the two sides to accept his reunification blueprint, had asked the three guarantor countries, Britain, Turkey and Greece, to intervene.

"The Secretary General has been talking to the guarantors, he's asked them to be here for this session of talks so that he could interact with them and I know he has interacted with them," he said. "I can't say anything else about anyone else he might have had contact with."

Other diplomat invloved in the process however said U.S. Secretary of State Colin Powell also phoned the Greek and Turkish foreign ministers to step up pressure for an agreement.

The Secretary General's plan calls for the rival Cypriot leaders to complete reunification talks by the end of March. After that, he would be authorized to fill in the blanks on any unresolved issues.

The completed deal would then be put to separate referenda in the Greek and Turkish parts of island in April. That would allow a unified Cyprus to join the European Union May first, if the referenda is approved.

If the process breaks down, only the internationally-recognized Greek Cypriot state would join the EU, further deepening Turkish Cyprus's isolation.

Cyprus has been divided since 1974, when Turkish forces invaded and occupied the northern third of the island. Turkey is the only country that recognizes the Turkish Cypriot entity.

The United Nations has maintained a peacekeeping mission along Cyprus's so-called Green Line for nearly 30 years.